A conventional image forming apparatus that uses an electrographic method is disclosed in JP Laid-Open Patent Application No. 2004-045481. The image forming apparatus includes a photosensitive drum, a charge device, an exposure device, a development device, a transfer device and a photosensitive body cleaning device. In the image forming apparatus, a surface of the photosensitive drum evenly charged by the charge device is exposed by the exposure device to form an electrostatic latent image. And then, the electrostatic latent image is developed by the development device to form a toner image on the photosensitive drum. After that, the toner image is transferred to a sheet by the transfer device, and is fixed on the sheet by the fuser device. After the toner image has been transferred, toner on the photosensitive drum is removed by the photosensitive body cleaning device.
In such an electrographic image forming apparatus, a toner disposal operation is performed to prevent problems such as unevenness of a print image density, decrease of dot reproduction, drum filming, fog and the like. That is, the toner is disposed to the photosensitive drum, and is collected by photosensitive body cleaning device when a consumption amount of the toner is equal to or less than a reference value.
However, pass-through of the toner easily occurs according to temperature in the apparatus. Herein, the pass-through is defined as follows: basically, toner disposed on the photosensitive drum is subject to be eliminated from the drum with a cleaning blade. However, some of the toner may go through between the blade and the photosensitive drum so that the toner remains on the surface of the drum. The phenomenon is defined the pass-through in the application.
One of objects of specific examples illustrated in the present invention is to reduce the pass-through of toner.